The present invention relates to a structure for mounting terminal plates each having a brush fastened thereto onto a bracket of a miniature motor. More particularly, it relates to a brush-mounting structure of the specified type which enhances the assembling job efficiency and prevents deterioration of brushes.
For the comparison with the present invention, a conventional miniature motor will be first explained with reference to FIGS. 1 and 2 which illustrate a cup-shaped metallic case 20 having the central portion of its top wall 21 projected outwardly and having a central hole 22 receiving a bearing 26. A recessed step 25 is formed at the inner peripheral edge of the open end of the case 20, except for portions accomodating the terminals of the motor. A rotor 27 has a plurality of coils 28, and a ring-shaped electrode plate 29 and a disk-shaped magnetic plate 30 are fixed to a rotary shaft 32 unitarily by the use of a synthetic resin portion 31. The rotor 27 is held on the rotary shaft 32 between the bearing 26, and a commutator 34 mounted so as to rotate unitarily with the rotary shaft 32. A permanent magnet 35 is fixed to a ring-shaped supporting member 36, and is disposed near the coils 28. The supporting member 36 has lugs 37 fitting in to the case 20.
A bracket 38 is attached to the open end of the case 20. An assembly on the bracket 38 will be described in detail with reference to a perspective view of FIG. 2. The bracket 38 is made of a substantially circular metal plate such as iron plate, and has a terminal portion 39 leading out from beneath the case 20. One surface of the metal plate 38 is wholly provided with an insulating film by coating, and a circuit portion 40 is formed on the insulating film. Terminal plates 42 made of a metal are soldered on the circuit portion 40, and their ends are formed into bent pieces 43, to which brushes 41 made of metal strips are fastened. The brushes 41 come into contact with the aforementioned commutator 34. On the circuit portion 40 of the bracket 38, a chip capacitor 49 for preventing electric noise, and the like are also soldered. Further, a member 48 for receiving the thrust load of the rotary shaft 32 is adhered onto the central part of the bracket 38.
As stated above, in the construction of this known miniature motor, the terminal plates 42 and other components are soldered in position. Soldering a member which includes a contact part often results in sulphurizing the contact due to the solder flux, a gas produced during the soldering operation, and the like, and waveform noise or the like may result. Moreover, the soldering operation forms an unstable factor as regards the job efficiency.